1. Field of Invention
This invention relates to annular slit restrictors in connection with pneumatic control systems.
2. Description of the Prior Art
A variety of different forms of fluid restrictors are used in fluid control systems. They are usually described as turbulent or laminar. The invention herein relates to laminar flow restrictors. Laminar flow restrictors are used when it is desired to have the flow coefficient proportional to the pressure differential across the restrictor over the whole range of useful pressure differentials.
Capillary tubes, flat or planar slits and annular slits are generally considered to be in the class of laminar restrictors. Annular slits remain laminar over a much larger pressure differential across the restrictors than capillary tubes do.
In summary, annular slit restrictors are the preferred form of a laminar restrictor. However the flow coefficient of an annular restrictor can vary by a factor of 2.4 due to the eccentricity of the central annular plug with respect to the defining annular hole. Further, the flow coefficient varies with the cube of the clearance within the annular slit.
The manufacture of precisely centered annular plugs of precise radial differences with respect to the annular hole has been so expensive that precise annular restrictors have been used sparingly in the past.
It is therefore a primary object of this invention to provide a novel means of making precisely centered annular plugs which are then inserted into defining annular holes and thereby produce precise annular slit restrictors.
It is desirable to have precisely centered annular slit restrictors with precisely controlled annular slit clearances that do not require machining capabilities that are better than are commercially available.